Tax
Form 1040 (Individual Income Tax Return)
The annual federal income tax return filed by individuals — the hub where wages, business income, investments, and deductions all come together.
Form 1040 is where everything lands: W-2 wages, Schedule C business profit, Schedule E rental and K-1 income, capital gains from Schedule D, and self-employment tax from Schedule SE. The supporting schedules do the detailed math; the 1040 totals it, applies deductions and credits, and settles the year against what was withheld or paid in estimates.
It's due April 15, with an automatic six-month extension to October 15 via Form 4868 — but the extension only extends the time to file, not the time to pay. Tax owed is still due in April, with interest and penalties accruing on any shortfall.
For business owners, the 1040 is downstream of the entity returns: partnerships and S-corps file in March precisely so K-1s exist in time for the owner's April return. When entity returns extend, the personal return almost always extends with them.
Common pitfalls
- Filing an extension without paying the projected balance — the extension stops the late-filing penalty, not interest or the late-payment penalty
- Filing in early April before all K-1s arrive, then amending — usually costlier than extending properly
- Overlooking state filing obligations in every state where K-1s or remote work created income
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